AQA A2 BIOL5 22nd June 2012
Biology exam discussion - share revision tips in preparation for GCSE, A Level and other biology exams and discuss how they went afterwards.
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Re: AQA A2 BIOL5 22nd June 2012Revision question guys! (easy one)
Describe and explain the role of receptors in regulating the rate of respiration during exercise (6marks)
Spoiler:Showchemo receptors are found in the aorta and carotid body. If we excercise we increase our metabolic activity, namely respiration. This produces co2. Co2 lowers ph of the tissue fluid in the blood by dissolving to form carbonic acid. This lower acidity is detected by the chemoreceptors, which send increase frequncy of nervous impulses to the cardio-accelotary centre of the medulla oblongata. This inturn sends increased waves of exitatory nervous implulses via the symapthtic nervous system to the sino atrial node. The sinoatrial node increases the rate at which the heart beats and so the cardiac output increases, leading to more co2 being exchenged in the alveoli of the lungs and back in to environment through exhalation. -
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Re: AQA A2 BIOL5 22nd June 2012Imagine a piece of DNA that is 10kb in length with two sites that can be cut by the same restriction enzyme to give fragments of 5kb, 4kb and 1kb. These fragments will be the only ones seen in a complete digestion. If the digestion is incomplete however, you will get some of these final fragments but still see fragments that have yet to be cut. For example, fragments that have not yet been cut at the restriction site that generates the 5kb and 4kb will be 9kb in length. Thus, when you look at an incomplete digest on an agarose gel, you will see 9kb, 5kb, 4kb and 1kb fragments. These add up to more that the original because the 9kb fragment has not yet been digested to give the 4kb and 4Kb fragments.(Original post by lilcherrydrop)
Can someone please explain why partial digestion of DNA fragment leads to DNA fragments adding up to more than the orignal DNA length? I understand you have larger fragments but why do you have more DNA quantity?
thanks!
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Re: AQA A2 BIOL5 22nd June 2012Fingerprinting:(Original post by Gibberish)
Can somebody explain genetherapy and genetic fingerprinting to me in simpleton terms? Preferably in marking points if it were a 6 marks question on both say?
Many thanksss
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DNA cut by Restriction enzymes
Separated by electrophoresis
Transferred (stuck on) to a nylon membrane - Southern Blotting
Radioactively marked Gene probes (complimentary to specific sequence/introns) are washed over the sheet, if a complimentary fragment is found, they form hydrogen bonds to it, otherwise they just get washed away
Gene probes fog up X ray film
Scientists look at the patterns of bands and the closer the pattern, the more likely the DNA is the same -
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Re: AQA A2 BIOL5 22nd June 2012My first attempt at an essay, thoughts?
http://www.scribd.com/doc/97649142/T...-organ-systems -
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Re: AQA A2 BIOL5 22nd June 2012Epic book: https://docs.google.com/file/d/1rR_f...kRE0wIWDb/edit(Original post by excell)
What's the best way to revise for essays?
I don't really have time to do practice ones as I have C4 maths tomorrow
Epic thing, whatever this is: https://docs.google.com/file/d/1rR_f...kRE0wIWDb/edit
The book's good for technique and the thing is good for practice
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Re: AQA A2 BIOL5 22nd June 2012Thanks but it says I don't have access to it?(Original post by uzumaki1107)
Epic book: https://docs.google.com/file/d/1rR_f...kRE0wIWDb/edit
Epic thing, whatever this is: https://docs.google.com/file/d/1rR_f...kRE0wIWDb/edit
The book's good for technique and the thing is good for practice
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Re: AQA A2 BIOL5 22nd June 2012I understand that incomplete digestion you'd have a longer piece as not yet been digested but wouldnt that mean you'd have 9kb instead of 5kb and 4kb? Why would you have both if the 9kb hasn't been digested? Confused(Original post by whc23)
Imagine a piece of DNA that is 10kb in length with two sites that can be cut by the same restriction enzyme to give fragments of 5kb, 4kb and 1kb. These fragments will be the only ones seen in a complete digestion. If the digestion is incomplete however, you will get some of these final fragments but still see fragments that have yet to be cut. For example, fragments that have not yet been cut at the restriction site that generates the 5kb and 4kb will be 9kb in length. Thus, when you look at an incomplete digest on an agarose gel, you will see 9kb, 5kb, 4kb and 1kb fragments. These add up to more that the original because the 9kb fragment has not yet been digested to give the 4kb and 4Kb fragments.
http://cambridgeacademic.blogspot.co.uk/
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Re: AQA A2 BIOL5 22nd June 2012Reverse transcriptase makes DNA from an RNA template - the DNA produced is called cDNA (complimentary DNA)(Original post by Gibberish)
I always forget the different between retriction endonucleases and reverse transcriptase? Can any one help?
Restriction endonuclease are enzymes that recognize specific palindromic base sequences and cut at these points via a hydrolysis reaction. the cut leaves small tails called 'sticky ends' which are unpaired bases at each end and can bind to other DNA if they have the complementary sequence. -
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Re: AQA A2 BIOL5 22nd June 2012can someone explain the answer to the question on the specimen paper about muscle contraction. i thought ATP was hydrolysed to recock the myosin heads instead it says it is hydrolysed to allow the power stroke/detach from myosin cross birdges.??????????
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Re: AQA A2 BIOL5 22nd June 2012Power stroke is basically what happens when Recock myosin head as it moves actin left, and ATP has two roles, the other role is to detach myosin head after power stroke(Original post by dc2012)
can someone explain the answer to the question on the specimen paper about muscle contraction. i thought ATP was hydrolysed to recock the myosin heads instead it says it is hydrolysed to allow the power stroke/detach from myosin cross birdges.??????????
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Re: AQA A2 BIOL5 22nd June 2012but the actual hydrolysis of atp is used to recock the myosin head. in the nt book- the power stroke is due to the adp molecule being released and the detatchment of the myosin head is due to the attatchment of atp.(Original post by jessplease)
Power stroke is basically what happens when Recock myosin head as it moves actin left, and ATP has two roles, the other role is to detach myosin head after power stroke
thanks for your help. -
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Re: AQA A2 BIOL5 22nd June 2012Oops, I actually sent you the same link twice :P PM me your email for the book and the other thing is here(Original post by excell)
Thanks but it says I don't have access to it?
https://docs.google.com/open?id=0B0m...lVXT3YyUWs5TDg -
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Re: AQA A2 BIOL5 22nd June 2012Hey, I'm doing the June 2011 past paper, and cannot seem to understand how to work out Q2 (c)(ii)
Link for the paper: http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN11.PDF
Page: 5
How do you work out the percentage?
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